THOUSANDS of political banners and signboards will be removed from the streets in the next few days to prepare for September's District Board elections. Political parties have been asked to remove advertising by the end of the week. The spaces, classified as ''key-spots'' for display of election publicity materials by the Boundary and Election Commission, will be reserved for candidates nominated for the District Board election. They will be allocated to different candidates by mutual consent or by lot after nominations close in mid-August. If parties do not remove banners, workers from the Urban Services Department and Regional Services Department will do so at the parties' expense. District Officers, who will serve as returning officers for the election, will co-ordinate the clean-up. Most parties said they would abide by the requirement.